A conventional means for electrically connecting a liquid crystal panel and a circuit board involves mechanically bonding an electrode formed on the liquid crystal panel and a contact formed on the circuit board under pressure with an anisotropic conductive rubber inserted therebetween.
In recent years, double-sided flexible wiring boards having a through-hole have been used in place of anisotropic conductive rubbers in order to improve the reliability of the connection between connecting terminals of liquid crystal panels and circuit boards.
FIG. 4 is a sectional diagram showing the main structure of a conventional flexible wiring board for double-side connection.
As shown in FIG. 4, this flexible wiring board for double-side connection 101 has a through-hole 102a formed at a given location in an insulating substrate 102 made from for example polyimide. Electrodes 121, 122 are formed on both sides of the insulating substrate 102, and these electrodes 121, 122 are connected to each other by a plating layer 103 applied via through-hole 102a. 
Such a double-sided flexible wiring board 101 can be bonded to a liquid crystal panel using an anisotropic conductive adhesive or an anisotropic conductive adhesive film with a higher connection reliability than obtained by the connecting means based on rubber and pressure, described above.
However, such a conventional flexible wiring boards for double-side connection 101 have the following problems.
As shown in FIGS. 5a and 5b, such a conventional flexible wiring board for double-side connection 101 has the problem that anisotropic conductive adhesive 104 runs off to the opposite side via through-hole 102a during thermocompression bonding to a liquid crystal panel 108, comprising a glass substrate 106 having an electrode pattern 107 formed thereon, for example, to cause smoothness loss or contamination. As a result, the reliability of the connection to other circuit boards is lowered.
The present invention was made to solve these problems of the prior art with the purpose of providing a flexible wiring board for double-side connection capable of improving the reliability of connection to circuit boards and a manufacturing process thereof.